Nights Getting Warmer Across United States, Analysis Finds

Find yourself waking up in the middle of the night and forced to turn on the air conditioning more often?

It's not you. It's a changing climate making nights warmer across the United States, according to an analysis of thousands of daily temperature highs and lows over the past 40 years by NBC News. The data comes from more than 500 weather stations.

The data shows that the ratio of record highs at night are outpacing record lows in most regions of the country. In the Northeast, stretching from Maryland to Maine, night-time record-highs now are occurring more than twice the record-lows.

Record highs should be hit about as often as record lows in a stable climate, a climatologist told NBC News. In other words, the ratio would be one to one.

But the ratio has been tilting toward more night-time record highs for decades, according to the data.

In the 1960s, the weather stations across the country recorded a nightime record-high to low ratio of 0.9. In the 1990s, the ratio was up to 1.4. This decade, through Sept. 6, the ratio is 1.7 — proof that nighttime record highs are occuring more often.

Want to see how your town or city has been affected by the rising night-time temperatures? Enter your zip code below.